Numerous devices have been devised, and some actually employed, for testing the physical condition of a human subject. The devices are employed for medical purposes, as well as to apprise an athlete of his physical condition during training. In a typical medical device, utilized in stress tests for physiological purposes, an electrocardiogram of a subject being tested is continuously taken. In addition, blood pressure is intermittently monitored, and in some instances respiration rate is measured. The oxygen transfer to the lungs of the subject is also measured. Other devices have been developed wherein elapsed time of a test is combined with heart beat pulses to derive an indication of a heart beat rate, as well as caloric consumption and total calories expended. Other devices which base calorie consumption only on heart rate are quite inaccurate because they do not take into consideration data required to calculate calorie consumption in accordance with variables which are known to effect calorie consumption viz: distance traveled, length of exercise time, resting heart rate, resting and exercise heart rate, weight of subject, change in heart rate in MET (multiples of metabolic need for sitting quietly) and oxygen consumed per minute per pound. Other systems have been devised wherein physical exertion parameters of a subject are determined as a function of the age of a subject, in combination with heart pulse frequency, to determine the stress on the heart.
Other devices have been proposed for monitoring physical condition of a subject in response to a signal derived from an electromechanical sensor adapted to generate an electrical pulse in response to each step taken by an individual while walking, running or jogging. In one particular system of this type, a computer counts the number of steps taken by the subject and, in response to a timing signal from a clock source, measures the rate at which the steps are taken. The computer continuously integrates the number of steps taken multiplied by the step rate over a time interval while the subject is being tested. The computer supplies signals to aural and visual outputs, to provide indications of the physical condition of the subject, and to apprise the subject as to whether he is achieving or exceeding predetermined levels associated with his physical parameters.
These prior art devices are frequently based upon information derived from two books written by Dr. Kenneth H. Cooper entitled "Aerobics", M. Evans and Company, Inc., New York, N.Y. (1968) and "The New Aerobics", M. Evans and Company, Inc., New York, N.Y. (1970). Dr. Cooper, in these books, defines the word aerobics as exercises that increase the supply of oxygen to various parts of the body of a subject. Exercises which typically fall into the category of aerobics are walking, jogging, running, hiking, climbing, tennis, cycling, weight lifting and swimming. Diligent pursuit of any of these exercises results in improved physical condition of a subject.
As previously indicated, the previously developed devices provide an indication of physical condition by relying primarily upon one of two variables, namely heart rate during exercise or distance traveled by a limb in exercise. Because heart rate is a prime indicator of physical stress, it is valuable to constantly monitor heart rate during exercise of a subject. Maximum heart rate in human subjects is dependent on age. Clinical evidence exists to indicate that optimum benefit from aerobic exercise is obtained when the cardiovascular system of the subject is exercised at a target heart rate range of between 75% to 85% of maximum heart rate for a particular subject for at least twelve minutes. However, clinical evidence developed by Dr. Azorides R. Morales, reported in September 1979, Medical World News, pps. 37 and 38, also exists to indicate that certain individuals, due to physical defects or condition, cannot use the standard 75% to 85% of maximum heart rate for their age, to calculate the target rate, without risk of heart damage to the subject. Certain of the prior art devices rely almost exclusively upon the heart rate monitoring to provide an indication of the physical condition of the subject. The other class of devices relies upon a measurement of distance and rate of distance covered to indicate the physical condition of the subject. These two classes of devices, however, have not generally provided the subject or physician with a complete analysis of the physical condition of a subject.